Fiberglass reinforced grating structures have several attractive features such as increased corrosion resistance, simple fabrication and installation, a high resistance to flame and sparks, slip-resistance, and a high strength-to-weight ratio. A disadvantage inherent in the design of fiberglass reinforced grating structures is the tradeoff of increased corrosion resistance at the expense of longitudinal strength. When uni-directional strength is important, pultruded grating is the preferred method of manufacture. Pultruded grating is typically produced by first making the load bars and cross bars by the pultrusion process and then assembling the bars together, resulting in a final product which is not an integral structure. Thus pultruded grating has a disadvantage of requiring secondary processing for the attachment and interconnection of the cross bars to the load bars as well as requiring the sealing of joints for corrosion resistance. Another disadvantage of pultruded grating is that the holes drilled in the load bars for insertion of the cross bars result in a decrease in strength of the structure. Another disadvantage of pultruded grating is it has inferior corrosion resistance due to the penetration of corrosive material through the intersections created by the drilled holes in the grating structure. Further, pultruded grating has reduced impact resistance in comparison to molded grating due to the lower resin content.
Prior art molded grating methods typically create grating having reinforcement material aligned in two directions and interwoven throughout the entire height of the grating for bi-directional strength. Thus where strength in one direction is primarily needed, molded grating has the disadvantage in that relatively expensive plastic resin material is not utilized in the most efficient structural manner. Another disadvantage of molded grating is that reinforcement is added to both load and cross bars in equal amounts for bi-directional strength while pultruded grating primarily reinforces the load bars for strength primarily in one direction. This results in molded grating being relatively more expensive and lower in strength in comparison with pultruded grating. In addition, the greater amount of expensive plastic resin used to manufacture the grating increases the processing time and costs. Further, molded grating has the disadvantage of allowing fluids to pool in the open areas of the grating.
Therefore, a more economical process is desired for producing a fiber reinforced plastic grating having an improved design which more efficiently utilizes expensive plastic resin and reinforcement material. In addition, an integrally made grating structure is also desired which eliminates the need for secondary processing. Furthermore, an improved fiber reinforced plastic grating article having greater structural strength and rigidity while having a lower weight yet maintaining corrosion and impact resistance is highly advantageous.